Emotional stress during pregnancy can have a detrimental impact on fetal development. Recent evidence indicates that the risk to the fetus may be due to a stress-induced reduction in uterine blood flow and subsequent fetal hypoxemia. To evaluate the relationship between maternal stress, uterine blood flow, and fetal oxygenation, chronically instrumented pregnant ewes will be exposed to daily stress using a Sidman avoidance paradigm. Uterine blood flow, renal blood flow, arterial blood pressure and heart rate will be monitored throughout the avoidance procedure to obtain a profile of the maternal cardiovascular response to psychophsiological stress. The maternal measures will be correlated with simultaneous recordings of fetal heart rate and blood pressure to determine the fetal cardiovascular response to stress-induced changes in maternal blood flow. Finally, fetal blood samples will be analyzed to examine the effect of maternal stress on fetal oxygenation. The results will provide considerable information on the physiological processes mediating the effects of maternal stress on fetal development.